**Abstract**

Analysis of volatile organic compounds (VOCs) in exhaled breath is non-invasive method and appears as a promising tool for metabolic monitoring. Diabetes is a complex syndrome, metabolic diseases that is characterized by hyperglycemia associated with major changes in lipids and proteins. The pathophysiology of the link between diabetes, hypertension, inflammatory syndrome and oxidative stress is complex. We conducted a study and applied quantitative analysis of exhaled ethylene and ammonia in patients with type 2 diabetes mellitus (T2DM) and a healthy control group. For breath gas analysis, a very sensitive CO2 laser photoacoustic spectroscopy (CO2LPAS) was applied. The concentration of exhaled VOCs differed between T2DM patients and healthy group, in particular, T2DM patients exhaled significantly higher amounts of ethylene and ammonia compared to healthy control group. The data obtained by the CO2LPAS system revealing that the increased breath VOCs has a close relationship with high glucose levels and with healthy complications.

**Keywords:** type 2 diabetes, exhaled breath, volatile organic compounds, ethylene, ammonia, CO2 laser photoacoustic spectroscopy

### **1. Introduction**

The analysis of volatile organic compounds (VOCs) represents a rapid and non-invasive method of early diagnosis. Some of the detected VOCs can be used as biomarkers for certain diseases or can reflect the metabolic profile of an organism and are presented in the exhaled breath, skin secretions, saliva, blood, urine and feces [1]. Breath analysis is considered to be a promising tool for noninvasive analysis of biochemical processes in the human body [2–5]. Exhaled breath contains both exogenous VOCs that come from environmental exposures as the ingestion of food, smoking cigarettes or/and air pollution, or endogenous VOCs that are produced by biological processes in the human body like oxidative stress (OS), inflammation, infectious disease. Breath analysis is currently used in the diagnosis of different pathologies, including gastrointestinal and liver disease, renal failure, lung disorders, cancer, and diabetes [6–8].

Diabetes Mellitus (DM) affects millions of people worldwide, and the incidence is increasing every year. Diabetes is a chronic condition characterized by hyperglycemia caused by a defect in insulin secretion or insulin action. Diabetes is a heterogeneous syndrome, characterized by a complex disorder in the regulation of the body's energy metabolism, which affects the use of carbohydrates, lipids and proteins, as well as other metabolisms [1–3]. The most prevalent type of DM is:

type 2 diabetes mellitus (T2DM), type 1 diabetes mellitus (T1DM) and gestational diabetes mellitus (GDM). According to International Diabetes Federation (IDF) 1 of 11 adults (20–79 years) have diabetes (463 million people), 1 in 2 adults with diabetes are undiagnosed (232 million people) and 2 in 3 people with diabetes lives in urban areas (310.3 million) [9, 10].

Individuals with T2DM presents increased risk for microvascular and macrovascular complications due to hyperglycemia. The complications related to diabetes are: eye disease (diabetic retinopathy), cardiovascular disease (one-third do half of all are diabetes related deaths), kidney disease, oral, nerve and/or vascular damage and diabetic foot complications (diabetic foot and lower limb complications affect between 40 and 60 million people with diabetes globally), diabetes-related complications of pregnancy (approximately 20.4 million of live births were affected by hyperglycemia in pregnancy in 2019) [9–14].

Studies over time have shown that oxidative stress contributes to the development and progression of diabetes, in T2DM particularly [15]. In diabetics, through hyperglycemia, hyperlipidemia, and hypertension is induced oxidative stress that affects multiple organs, leading to various complications including coronary artery disease, stroke, neuropathy, nephropathy, retinopathy [16, 17].

The aim of this chapter is showing the role of breath analysis in the evolution of type 2 diabetes mellitus by measuring ethylene and ammonia as oxidative stress breath biomarkers at T2DM and healthy subjects, using a CO2 laser photoacoustic spectroscopy (CO2LPAS) system. At the same time, it was determined the glycated hemoglobin HbA1c and blood glucose levels. Breath tests were compared between the two groups (healthy and with T2DM) to see if the breath analysis can discriminate between diabetic and healthy subjects, and if the breath tests are in accordance with blood tests.
